Non-destructive methods are required in the case of numerous material tests. Examples are the surfaces of components made from metal frequently exposed to an environment that effects corrosion, oxidation, diffusion and further ageing processes. Cracks can also be caused in the surface of the component by mechanical stresses.
This also applies, for example, to the moving and guide blades of a gas turbine that are exposed, in particular, to crack formation at their surface owing to mechanical and thermal loads. Non-destructive test methods are required in order to be able to check the current state of such a blade wheel.